1. Technical Field
This disclosure generally relates to a technology for controlling power supply of an image forming apparatus and specifically relates to a technology for controlling power supply of a power source of the image forming apparatus when a peripheral apparatus is newly connected to the image forming apparatus.
2. Description of the Related Art
Generally, in an image forming apparatus of an electrophotographic type, a short startup time is required for making a printing ready immediately after power is turned on or when an energy saving mode is returned to an operation mode. The image forming apparatus is, for example, a copying machine and a printer. The image forming apparatus includes an image forming unit that includes a photosensitive member, a charging unit, an exposing unit, a developing unit, a transfer unit, and the like that are arranged in the vicinity of the photosensitive member, and a fixing device for fixing a toner image transferred onto a transfer paper by the transfer unit. The fixing device is provided with a fixing roller installed with a heater. A heater control device that controls energization to the heater is further provided to maintain the temperature of the fixing roller constant. Commonly, a factor that affects a startup time most is time for warming up at startup of the fixing device. Accordingly, if the time for warming up the fixing device can be shortened, the startup time before printing becomes ready can also be shortened.
Furthermore, in recent years, ordinary image forming apparatuses can be connected to outside apparatuses via a network, and an image forming apparatus is often used with power on all the time. Therefore, it is important to make the time taken for returning from an energy saving mode shorter.
Shortening of startup time has been conventionally performed by providing an auxiliary power device that supplies rechargeable DC power. When quick startup is needed, power is supplied to loads inside the apparatus from both the main power source and the auxiliary power source without drawing excess load from a commercial alternating-current (AC) power supply line serving as a primary power source. Quick startup of the fixing device can be performed by supplying sufficient power to the fixing device with the use of the auxiliary power device that uses a capacitor such as an electrical double-layer capacitor and supplies rechargeable DC power.
Even though a capacitor such as an electrical double-layer capacitor is used, deterioration in performance sometimes occurs. For example, when the capacitance of the capacitor decreases owing to performance deterioration, there are problems that electric energy to be supplied becomes insufficient and the proper function of the capacitor cannot be sufficiently realized. Accordingly, the image forming apparatus generally includes a unit that monitors common deterioration in performance of the capacitor, and when performance deterioration is detected, the capacitor is immediately regarded as abnormal, and countermeasures that recommend a user to exchange the capacitor are taken by giving a warning with a service call and the like.
However, when the determination of deterioration in performance of the capacitor is not proper, a warning is given even though the capacitor is still usable. Hence, a technology for determining when a warning is given is disclosed in Japanese Patent Application Laid-Open Publication No. 2005-221774. In the technology, an image forming apparatus includes a unit that detects performance deterioration of the capacitor as well as a unit that detects productivity reduction of image formation and controls timing for giving a warning using logical multiplication (AND). Namely, when the logical multiplication between detection of performance deterioration of the capacitor and detection of productivity reduction is established, it is determined that a warning needs to be given.
However, there are various system structures (combinations of functional units) for an image forming apparatus. Even though the same printer engine (printing mechanism to form images on paper) is used, the system scale and the power consumption vary depending on whether other units such as a document image reading unit (scanner), an automatic document feeder (ADF), an additional paper feeder (paper bank), a large capacitance tray (LCT), or a finisher are provided. When deterioration in performance of the capacitor becomes worse to some extent, startup is often delayed due to insufficiency of auxiliary power in an image forming apparatus in a large system and it causes deterioration in the usability of a user. On the other hand, a delay in startup caused by insufficiency of auxiliary power hardly occurs in an image forming apparatus in a small system, which does not impair the usability of a user. Even though performance deterioration of a capacitor becomes worse to a significant degree, the usability of a user is not impaired badly in an image forming apparatus in a small system, and it is possible to continuously use the auxiliary power device in the small system.